1. Field of the Invention
The present invention relates to a device for generating a control signal of a tuner system, and more specifically to a device for generating a tuning frequency set command signal of a tuner system which is provided with a function of automatic channel scanning.
2. Description of Background Information
There is a type of tuner having a function of automatic channel scanning in which the automatic scanning of the tuning frequency is performed until a signal from a station is captured. As an example, tuners equipped with a PLL synthesizer circuit have this automatic channel scanning function. In the case of the tuner of this type, the use of an additional switch for commanding the automatic channel scanning is eliminated because such an increase in the number of control switches would deteriorate the easiness of handling of the tuner. Therefore, it is general to assign the function of commanding the automatic channel scanning, to the up and down command switches or buttons for the manual tuning operation. If the up or down switch is pressed for a period shorter than a predetermined length of time, the tuner selects the manual tuning operation in which the scanning of the tuning frequency is effected at a constant speed until the pressure on switch is removed. On the other hand, if the up or down switch is pressed for a time period longer than the predetermined length, the tuning operation is switched to the above mentioned automatic channel scanning.
However, in the case of a conventional device for generating a tuning frequency set command signal, there was a drawback that if the up or down switch is pressed more than one time within the predetemined time period, then the automatic scanning mode is selected against the operator's will, even if the duration of each time of pressing is shorter than the predetermined period.